An American soldier has been sentenced to nine months in a military prison after he admitted to shooting at unarmed Afghan civilians. Twelve US troops have been charged with killing innocent civilians and some are accused of mutilating their bodies. Staff Sergeant Robert Stevens, 25, has begun the sentence of nine months' confinement at a US military base in Washington state. Stevens was part of a team of 12 soldiers who it is claimed were a rogue unit targeting unarmed civilians for sport. Five of the soldiers are accused of murder after three Afghan men died. It is claimed the soldiers threw a grenade and opened fire on them. Some of the soldiers are also accused of keeping body parts of dead Afghans, taking photos of corpses and of using drugs.